Which of the following is the smallest unit of a compound that retains the chemical properties of that compound?

• A. Element
• B. Atom
• C. Ion
• D. Molecule

Answer: (D)

Verified step by step guidance

1. Understand the definitions of the terms given: An element is a pure substance consisting of only one type of atom; an atom is the smallest unit of an element that retains its chemical properties; an ion is an atom or molecule with a net electric charge due to loss or gain of electrons; a molecule is two or more atoms chemically bonded together, representing the smallest unit of a compound that retains its chemical properties.
2. Recognize that a compound is a substance formed when two or more different elements are chemically bonded together.
3. Recall that the smallest unit of a compound that retains the chemical properties of that compound must contain more than one atom bonded together, which excludes single atoms or ions alone.
4. Identify that a molecule fits this description because it consists of two or more atoms bonded together, representing the smallest unit of a compound that maintains its chemical identity.
5. Conclude that among the options, the molecule is the correct choice as it is the smallest unit of a compound retaining the compound's chemical properties.